Question

Abigail has a spinner with 15 equal sections, each labeled with the name of a different animal. If Abigail spins it 234 times, what is the probability that she will land on a pig or giraffe? (HINT: first, find the probability of landing on those animals. Then, apply that to the amount of times she is going to spin.

Answer 1

We can assume that each one of the 15 sections has one of the animals. And because each one of the 15 sections is equal, the probability of landing in any animal must be the same, this means that the probability of landing on a given animal must be:

p = 1/15

Then the probability of landing on a pig is:

p1 = 1/15

The probability of landing on a giraffe is:

p2 = 1/15

The probability of landing on a pig, or a giraffe, will be equal to the sum of the two individual probabilities

P = p1 + p2 = 1/15 + 1/15 = 2/15.

So each spin has a probability of 2/15

This means that the probability of NOT landing on these animals must be 13/15.

Now, the probability of not landing on these animals in 234 different spins will be:

P´ = (13/15)^234 = 2.9*10^(-15)

Then the probability of landing on one of these animals, in at least one of the 234 different spins, will be:

prob = 1 - P´= 1 - 2.9*10^(-15) = 0.999999...